Recovery of certain metal salts



Patented June 2, 1942 UNITED STATES: PATENT 1 OFFICE RECOVERY OF METAL SALTS Eduard Fiirber,

New Haven, Conn, assignor to Polyxor Chemical 00., Inc., New

Haven, Conn.,

a corporation of New Jersey Serial No. 288,379

' 8 Claims.

My invention relates to various salts, for example nickel chloride hexahydrate, which are produced initially in solution commonly, and which can be recovered from solution in a watersoluble form by crystallization, but when recovered from solution by the customary commercial evaporation procedures, the residue ration contains a considerable'percentage of insolubles. For example, nickel chloride hexahydrate obtainedby customary evaporation processes, has mixed with it a considerable percentage of basic nickel chloride which is insoluble in water.

Crystallization is, of course, a slow and rather delicate process commercial production and is to be avoided when possible.

More specifically, the'invention relates to those salts of which the metal is a metal having an atomic weight not less than that of nickel and not greater than that of copper (i. e., isnickel, cobalt or copper), and of which the acid is hydrochloric, formic or sulphuric acid.

I have discovered a procedure whereby the customary evaporation processes (for example, concentration by heat followed by final evaporation and dryingon rotating metal drums) can be used to expel the water from solutions of these salts withoutieaving. a percentage of insolubles. The metal salts thus obtained may be contaminated with small amounts of impurities, as will appear hereafter, but these are soluble and they are of such a nature and comprise such a small percentage of the total residue that they are unobjectionable for various uses to which the metal salts are put.

Briefly, I add to a solution of the metal salt, a salt or salts which, under the conditions existing during the evaporation, will cause the association of the dissociated radicals of the metal salt that is not well adapted for after evaporadicals,

will associate into only one or more solubles or vaporous compounds. Any such vaporous com pound that may be formed (that is to say, a compound that is vaporous at the evaporating temperat-ure) escapes during the evaporating procedure and accordingly does not enter into the solid residue, excepting as it mayappear in, say, the residual soluble hydrate form of the metal salt as in the case when water is formed from some of the dissociated radicals that, except for and the water of the solution into only compounds that are water-soluble or vaporous-at .the

evaporating temperature. It is to be understood that herein I use the term vaporous as including gaseous. 'Instead of adding such a salt to the solution directly, I may of course add to the solution a material or materials which, by reaction with the solution or otherwise, will produce such a salt, and thus by indirection.

It will be apparent that the nature or'type of the action of the added salt is immaterial, and also that the particular cons 'tuents of the initial solution or the particular products of the evaporation with wliich'the added salt reacts "is imadd thedesired salt the action brought about by the added salt, would enter into other compounds. Also, any such soluble but residue-contaminating compounds as may be formed need represent only such a small degree of contamination as to be unobjectionable 'inmany instances, as pointed out before. Also, the added salt may be selected for its ability to act as a buii'er substance preventing losses of volatile acids like hydrochloric from chlorides and formic acid from formates, or to inhibit any action of small amounts of, say, liberated sulphuric acid on the metal of the surface on which the solution isto be dried, As further examples, the salt to be added to the solution may be selected for its ability to act by inhibiting any catalytic reaction which otherwise an insoluble salt of the metal, or as a catalyst producing only the soluble-metal salt desired, or

leading. to the production of a soluble substance or substances in lieu of an insoluble product otherwise appearing.

In general therefore the form or nature of the action or actions of theadded salt is not of primary importance salt or salts I employ one or more of the water- 'soluble alkali salts of organic acids or of the usually these temperatures are about to'12 5 such acids, and by economy) salts of C. I have discovered that the quantities of such salts required are small.

the free radicals then in the solution would produce to my invention. As the added that are not readily volatil-- As a specific example of my invention, I take a water solution of sufficient nickel sulphate to solution may be deposited on the outside of a rotating heated metal drum on which it is further evaporated until the solute appears as dry flakes v which canbe scraped off the drum easily as the drum rotates. These flakes comprise nickel sulphate hexahydrate with a small percentage of organic. impurity; they are completely soluble in water and are not hygroscopic;

another specific example, I take a water solution containing nickel chloride suflicient to produce about 120'grams of nickel chloride hexahydrate, and to this add one gram of sodium lactate or potassium lactate. On expelling the Water, say by heat in the manner indicated before, a completely soluble product results that contains nickel chloride as a hexahydrate and which maintains its dry form and does not form lumps when kept for a long time.

Again, to a water solution containing suflicient cupric chloride to produce 100 grams of the hydrate, I add about two grams of sodium tartrate, and upon evaporation to apparent dryness, as

by hot air blown through the solution or by heating in contact with metal surfaces as before, a

. thesolutionto completely soluble residue containing watere soluble cupric chloride hydrate is obtained.

Again, the sodium salt of an organic acid like propionic may be added to a solution of nickel sulphate, in generally similar proportions, with similar results, and with various solutions, e. g.

chloride solutions, similar results can be obtained.

by earth-alkali, e. g. calcium, salts of the organic acids. It will be understood of course that my invention is not limited to the matters of details appearing in the specification above except as appears hereinafter in the claims. 1

Iclaim: 1. The method of obtaining the salt of a metal of the group consisting of those metals the atomic weights of which are not less than the atomic weight of nickel and not greater than the atomic weight of copper and an acid of the group consisting of hydrochloric, formic and sulphuricacids, without substantial admixture of a water-insoluble substance, which method consists in adding, to a solution of the metal salt, a relatively small quantity of one or more substances selected from the group consisting of the water-soluble alkali and alkaline earth metal salts of organic acids, and thereafter obtaining substantially all of the metal salt by evaporating dryness.

2. The method of claim 1, characterized by the fact that the added substance consists at least inpart of a lactate.

3. The method of claim 1, characterized by the fact that the added substance consists at least in part of a propionate.

4. The method of claim 1, characterized by the fact that the added substance consists at least in part of a tartrate.

5..The method of claim 1, characterized by the fact that the metal salt is nickel sulphate and the added substance at least includes a substance selected from the group consisting of sodium lactate and sodium propionate, the proportions,

by weight, being suflicient of the metal salt to produce about 130 parts of the hexahydrate thereof, to about one part of said added substance.

-6. The method of claim 1, characterized by the fact that the metal salt is nickel chloride and the added substance at'least includes a salt potassium lactate; the

of the group consisting of sodium lactate and being sufficient of the first ,to produce 120 parts of the hexahydrate thereof, to-about one part of the second.

7. The method of claim 1, characterized by the fact that the metal salt is cupric chloride and the added substance at least includes sodium tartrate, the proportions, by weight, being sufflcient of the first to produce 100 parts of the hydrate thereof, to about two parts of the second.

8. The method of claim 1, characterized by the fact that the metal salt is a chloride and the added substance at least includes a calcium salt.

EDUARD FARBER.

proportions, by weight, 

